Abstract: To achieve the green and controllable preparation of food-grade lignin nanoparticles (LNPs), this study utilized lignin from corncobs as the raw material and employed an ethanol-water based antisolvent method to prepare LNPs. The effects of key process parameters, including initial lignin concentration, rate of water addition, preparation temperature, and stirring rate, on the particle size, morphology, and ζ-potential of LNPs were systematically investigated. A predictive model for the size of spherical LNPs was established using response surface methodology, and the chemical structure, storage stability, and antioxidant activity (ABTS⁺· and DPPH radical scavenging capacity) of LNPs with different sizes were further examined. The results indicated that initial lignin concentration, rate of water addition, preparation temperature were critical factors influencing the particle size and morphology of LNPs. Spherical LNPs with controllable sizes ranging from 50 to 300 nm were successfully prepared within the parameter ranges of 1~6 mg/mL (initial lignin concentration), 1~24 mL/min (rate of water addition), and 20~65 ℃ (temperature). Notably, nanospheres with a single-hole structure were obtained at 65 ℃. FT-IR analysis confirmed that the chemical structure of lignin remained unchanged during nanoparticle formation. The as-prepared LNPs exhibited excellent long-term storage stability, with no significant changes in size or morphology after 60 days at 25 ℃. Antioxidant assays revealed a distinct size-dependent activity, wherein smaller LNPs displayed stronger radical scavenging capacity. This study provides a theoretical foundation and technical pathway for the valorization of agricultural waste-derived lignin and the development of natural antioxidant nanomaterials.